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  <TITLE>Qubiter: Introduction</TITLE>
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<H1>
  Introduction
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<P>
<B>XCode</B> is an application (Integrated Development Environment) produced
by Apple Inc. It provides an interface for the gcc (GNU) compiler. XCode
is available for free at the Apple website.
<P>
<B>Clapack</B> is a library of linear algebra subroutines. It was produced
by translating the Fortran library called Lapack into C via a tool called
f2c. Clapack is available for free at
<A HREF="http://www.netlib.org">www.netlib.org</A>. <U>Clapack is automatically
included (as the vecLib Framework) in the standard installation of MacOS
X .</U>
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Qubiter (US Patent
<A HREF="http://www.google.com/patents?id=b8ULAAAAEBAJ&amp;dq=patent:6456994">6,456,994
</A>) is a computer program that can decompose an arbitrary unitary matrix
(Well, as long as it's not too big) into a SEO (sequence of elementary
operations---operations such as controlled-nots and qubit rotations). Such
SEOs are used to manipulate an array of quantum bits (i.e. a quantum computer.)
&nbsp;The mathematics behind Qubiter is explained in: "A Rudimentary Quantum
Compiler(2cnd Ed.)", by R. R. Tucci, arXiv eprint
<A HREF="http://www.arxiv.org/abs/quant-ph/9902062">quant-ph/9902062</A>.
Additional references can be found
<A HREF="http://www.ar-tiste.com/qubiter.html">here</A>. Qubiter is brought
to you courtesy of the Artiste Company, makers of
<A HREF="http://www.ar-tiste.com">Quantum Fog</A>.
<P>
<FONT COLOR="Red">VERY IMPORTANT: Before starting to use Qubiter 1.11, you
must first read and agree with the Qubiter license. You can find it in the
file entitled "Qbtr1.11_License.txt"</FONT>
<P>
In its current version 1.11, Qubiter is fairly crude---a pure C++ program
with no GUI.&nbsp;It's just a research tool, so don't expect too much. The
Qubiter 1.11 distribution includes an&nbsp;XCode 2.4 project file. Qubiter
is linked to the Clapack library.
<P>
Since Qubiter 1.11 is pure C++, you don't need XCode, or even Mac OS X to
use it: you can run Qubiter on any platform for which you have a C++ compiler.
However, if you don't use XCode, you will have to write your own makefile
or project file. Furthermore, if you do not use MacOS X, you will have to
install the Clapack library in your computer, if it isn't installed already,
as it is in Macs.
<P>
Henceforth we will use "MATNAME" as a prefix in file names. &nbsp;For example,
we will speak of a file called "MATNAME-engl.in". You should replace MATNAME
by a name that identifies the particular matrix being analyzed. For example,
you might use "FT3bits-engl.in" instead of "MATNAME-engl.in" if you are dealing
with 3 bit Fourier Transform matrices.
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